It's a nice language and a nice platform. The new ASP.NET MVC and EntityFramework stuff is very nicely done too. The community is in the lift as well thanks to the professional stackoverflow network and initiatives like NuGet. It really isn't a bad place to work in. Same deal goes with Visual Basic. Same power, different (imo easier to read, more annoying to write) syntax.

But for a low-budget startup the licensing costs are what'll get you in the long run. Stick with something free to use like ruby, javascript, php, etc.